Percent Decrease
Value after a percentage decrease.
Formula
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Example
$50 down 20% = $40
How it works
A percent decrease means you keep only the part of the original value that is left after the drop. If the decrease is p as a decimal, then the remaining fraction is 1 - p, so multiplying the original value by that amount gives the new value. This works because subtracting a percentage reduction is the same as removing that fraction of the starting amount.
When to use it
Use this when something gets cheaper, smaller, shorter, or reduced by a stated percentage. It appears in discounts, population decline, test score drops, and any situation where you need the value after a decrease.
Worked example, step by step
Original price = $80 Decrease = 15% = 0.15 new = old(1 - p) new = 80(1 - 0.15) new = 80(0.85) new = 68 Final answer: $68
Common mistakes to avoid
- Using 1 + p instead of 1 - p
- Forgetting to convert the percent to a decimal before calculating
- Subtracting the percent from the original number directly, such as 80 - 15, instead of taking 15% of 80
Did You Know?
Discounts never stack the way shoppers expect: 20% off then another 20% off is a 36% cut, not 40%.
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